diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 321dbf9..8776e07 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -644,6 +644,8 @@
   set ts=8
   set grepprg=some\ text
   assert_equal('some text', &grepprg)
+  &grepprg = test_null_string()
+  assert_equal('', &grepprg)
   set grepprg&
 enddef
 
diff --git a/src/version.c b/src/version.c
index c6259bc..231640c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    168,
+/**/
     167,
 /**/
     166,
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 6865ba1..480f1ec 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -625,7 +625,11 @@
 		    --ectx.ec_stack.ga_len;
 		    tv = STACK_TV_BOT(0);
 		    if (tv->v_type == VAR_STRING)
+		    {
 			s = tv->vval.v_string;
+			if (s == NULL)
+			    s = (char_u *)"";
+		    }
 		    else if (tv->v_type == VAR_NUMBER)
 			n = tv->vval.v_number;
 		    else